Distillation columns as used in refineries and chemical companies are tower-like structures, which are substantially built up of a cylindrical outer wall having a height in the order of 100 m and more, whereby the outer wall is provided with rings which are welded to the inner side of said wall in regularly spaced-apart relationship, on which rings the distilling dishes are supported. The outer wall of said columns is provided with manholes at regular intervals, through which access can be gained to the inside of the column for inspecting the dishes and for carrying out repairs and installation work. All the materials needed for carrying out various activities, such as the installation of new dishes, the carrying out of repairs to existing dishes and the modification of dishes, must be introduced into the inside of the column via said manholes. In order to be able to carry out these activities more quickly, operators have proceeded to carry out these activities simultaneously in several sections the last few years. This constitutes a safety hazard, however, because several people are working one above the other and it regularly happens that tools, welding spatter or screw materials fall down the column. In order to overcome this problem operators have proceeded to place wooden planks on the rings, which planks are to function as a temporary working platform. The drawbacks of these wooden working platforms are that they constitute a fire hazard, that they are not strong enough, that refuse of the materials being used is not possible, that the column section is not entirely covered in an optimum manner, and that there is a risk of the planks present on the rings turning over. What makes matters worse is the fact that the planks being used may only have a limited width, since they must be introduced into the column through said manholes, and generally the diameter of said manholes is only in the order of 50 cm.